Electronic devices may communicate with one another. Connectivity amongst the different electronic devices may be facilitated by using physical connectors (such as cables). The connectors may have various parameters such as: size, labeling, interface parameters, structure, etc. Interface parameters may include: number of connectivity pads (e.g., pins), the layout of the connectivity pads and their physical size, etc.
Further, there are many different types of connectors. Examples of different standard connector types include, but are not limited to: an eight position-eight conductor (8P8C) modular connector with eight positions, which may be used in Ethernet® communications; a D-subminiature electrical connector commonly used for the RS-232 serial port on: modems, computers, telecommunications, test and measurement instruments; an HDMI (High-Definition Multimedia Interface) connector compact audio/video interface for transferring uncompressed video data and compressed/uncompressed digital audio data from a HDMI-compliant device (“the source device”) to a compatible computer monitor, video projector, digital television, or digital audio device; a Universal Serial Bus (USB) connector (e.g., USB 2.0 has a 4-pin connector; USB 3.0 has 9 pins surrounded by a shield); a Power connector which may include a safety ground connection as well as the power conductors for different household equipment; a RF Connector used at radio frequencies having constant impedance of its transmission line; a R-TNC (Reverse threaded Neill-Concelman) connector used for Wi-Fi antennas; a BNC connector for used in radio and test equipment; DC connector which may supply direct current (DC) power; Hybrid connectors which may have housings with inserts that allow intermixing of many connector types, such as those mentioned above; optical fiber connectors; and many more different types of connectors.
Each field/system/device may have a standard or custom electrical cable that has different parameters. Example of electrical cable's parameters may include any one, any combination or all of: length; cable diameter; number of inner-wires; inner-wire coloring; inner-wire diameter; cable color; labeling; insulation/shielding; and winding/twisting.
A cable may comprise two or more wires running side by side and bonded, twisted, or braided together to form a single assembly. Any current-carrying conductor, including a cable, radiates an electromagnetic field. Likewise, any conductor or cable will pick up energy from any existing electromagnetic field around it, and in the first case, may result in unwanted transmission of energy that may adversely affect nearby equipment or other parts of the same piece of equipment; and in the second case, unwanted pickup of noise that may mask the desired signal being carried by the cable.
There are particular cable designs that minimize electromagnetic pickup and transmission. Three of the principal design techniques are shielding, coaxial geometry, and twisted-pair geometry, for example. Shielding makes use of the electrical principle of the Faraday cage. The cable is encased for its entire length in foil or wire mesh. In some cables a grounded shield on cables operating at 2.5 kV or more gathers leakage current and capacitive current.
Coaxial design may help to further reduce low-frequency magnetic transmission and pickup. In this design, an inner conductor is surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables also have an insulating outer sheath or jacket. The foil or mesh shield has a circular cross section and the inner conductor is exactly at its center. This causes the voltages induced by a magnetic field between the shield and the core conductor to consist of two nearly equal magnitudes which cancel each other.
Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources. A twist rate (also called pitch of the twist, usually defined in twists per meter) makes up part of the specification for a given type of cable. Where nearby pairs have equal twist rates, the same conductors of the different pairs may repeatedly lie next to each other, partially undoing the benefits of differential mode. For this reason, it is commonly specified that, at least for cables containing small numbers of pairs, the twist rates must differ.
Twisted pair cables may be shielded in an attempt to prevent electromagnetic interference. Because the shielding is made of metal, it may also serve as a ground. Typically, a shielded or a screened twisted pair cable has a special grounding wire added called a drain wire which is electrically connected to the shield or screen.
This shielding may be applied to individual pairs, or to the collection of pairs. When shielding is applied to the collection of pairs, this is referred to as screening. Shielding provides an electric conductive barrier to attenuate electromagnetic waves external to the shield and provides conduction path by which induced currents can be circulated and returned to the source, via ground reference connection.
A few examples of different field electrical cables can include: Category 1 cable (Cat 1) or voice-grade copper, which is a grade of unshielded twisted pair cabling designed for telephone communications; Cat6 (Category 6 cable), which is a standardized cable for Gigabit Ethernet and other network physical layers; an HDMI cable of about 5 meters (16 ft.), which can be manufactured to Category 1 specifications by using 28 AWG (0.081 mm2) conductors or by 24 AWG (0.205 mm2) conductors, an HDMI cable can reach lengths of up to 15 meters (49 ft.).
Individual USB cables may run as long as 5 meters for 12 Mbps connections and 3 meters for 1.5 Mbps. With hubs, devices can be up to 30 meters away from the host, the USB 2.0 type cable has two wires that supply the power to the peripherals (−/+)5 volts (red color) and ground (brown) and a twisted pair (yellow and blue) of wires to carry the data. On the power wires, a computer can supply up to 500 milliamps of power at 5 volts; etc.
Although some cables and connectors have standard specification (parameters), others may have a custom tailored-made specification. Original equipment manufacturers (OEM) as well as automotive and defense industries often require custom cables and/or connectors for their equipment, for example. Tailoring may include any one, any combination, or all of the following different variables: lengths, insulation coloring, labels, sizes, diameter, etc. Further, the cable harnesses may be tailored. For example, a cable harness may have two or more connectors, connected by any topology and connection scheme according to a customer demand.